facetwp yoast seo filter robots

<?php
/** basic check to modify robots when facets are selected during pre-load **/
add_filter( 'wpseo_robots_array', function( $robots, $class ) {
    if ( function_exists( 'FWP' ) && !empty( FWP()->ajax->url_vars ) ) {
      $robots['index'] = 'noindex';
      $robots['follow'] = 'nofollow';
    }
    return $robots;
}, 10, 2);